1. Field of the Invention
The present invention relates to a method of producing a semiconductor device such as a semiconductor dynamic sensor for detecting an amount of acceleration, pressure or the like.
2. Related Arts
A semiconductor acceleration sensor is, as shown in FIGS. 31 and 32, conventionally composed of a rectangular plate-like silicon substrate 61, through grooves 62 formed on the silicon substrate 61 (a silicon chip), a rectangular frame (a thick portion) 63 formed at an outer side of the through grooves 62, and a rectangular weight (a thick portion) 64 formed at an inner side of the through grooves 62. The frame 63 and the weight 64 are connected by thin beams 65 to 68, and strain gauges 69 to 72 for detecting an amount of acceleration are formed on the beams 65 to 68, respectively. The silicon substrate 61 is bonded to a ceramic substrate 73 by utilizing adhesives 74 after dicing. That is, the lower face of the frame 63 and the upper face of the ceramic substrate 73 are bonded to each other through the adhesives 74.
In processes of manufacturing the acceleration sensor, as shown in FIGS. 33 and 34, firstly, thin portions 75 on which strain gauges are formed are formed on a silicon wafer 76. Each thin portion 75 corresponds an area where beams and through grooves are to be formed to form one sensor chip. The silicon wafer 76 is attached to a self-adhesive sheet 77 for dicing, and then, it is cut to be divided into sensor chips along dicing lines Ld by a dicing blade 80.
On the other hand, as shown in FIGS. 35 and 36, a semiconductor pressure sensor is conventionally composed of a square plate-like silicon substrate 90, a recess 91 formed on the silicon substrate 90, and a diaphragm 92 formed at the bottom of the recess 91. On the diaphragm 92 are formed strain gauges 93 to 96 for detecting an amount of pressure applied to the diaphragm 92. Further, the silicon substrate 90 is joined to a glass base 97. On the back face of the glass base 97, a vapor deposition layer 98 made of metal is formed, and is joined to a metallic stem 99 through a solder layer 100.
In processes of manufacturing the pressure sensor, diaphragms 92, each of which forms one pressure sensor, are formed on a silicon wafer 101. As shown in FIG. 37, the silicon wafer 101 is bonded to a glass plate 102 for forming the glass base 97. The back face of the glass plate 102 is attached to a self adhesive sheet 104 through a vapor deposition layer 103 made of metal. Thereafter, the silicon wafer 101 and the glass plate 102 are cut into sensor chips along dicing lines by a dicing blade 105.
In the dicing process of the semiconductor acceleration sensor, however, cracks 78 and chippings 79 of the silicon wafer 76 occur at edge portions cut by the dicing blade 80 as shown in FIG. 33. Therefore, as shown in FIG. 38, thus obtained sensor chip 81 has the cracks 78 and the chippings 79 on outer circumferential faces (dicing portions) thereof. Especially in the semiconductor acceleration sensor, as shown in FIG. 32, a width W.sub.F of the frame 63 has been becoming narrow to miniaturize the sensor chip in recent years. Accordingly, the frame 63 becomes liable to be broken due to the cracks 78 and the chippings 79, and inferior adhesion of the frame 63 becomes liable to occur when the sensor chip is mounted.
Further, in the dicing process of the semiconductor pressure sensor, as shown in FIG. 37, the dicing blade 105 used for thick plates such as the glass plate 102 is liable to generate big chippings 106 compared to the other dicing blade which is used for thin plates such as a silicon wafer. In this case, an exfoliation of the vapor deposition layer 103 formed on the back face of the glass plate 102 accompanies the chippings 106, thereby resulting in inferior junction between the glass base 97 and the metallic stem 99 in the sensor chip shown in FIG. 36.